Withdrawing cores from molded conduits



1 l a March 927 T. E. MURRAY WITHDRAWING CORES FROM MOLDED CONDUITSFiled Sept. 17', 1924 avwe'ntom 7710/17/15 5 Mar/"(1y Patented Mar. 1,192 7.

UNITED STATES PATENT OFFICE.

THQMAS E. MURRAY, OF BROOKLYN, NEW YO RK. q

wrrnnimwme corms FROM MOLDED CONDUITS.

Application filed September 17, 1924. SerialNo. 738,151.

In an application of Thomas E. Murray,

No. 670,423, now Patent 1,556,869, dated composition that when pulledlongitudinally it will contract transversely to break its adhesion tothe surrounding material and permit its withdrawal. Such cores aregenerally made of high grade rubber composition to secure the necessaryresiliency. When the conduit is of considerable length or is curvedlongitudinally the' withdrawal of the core requires a very strong pull,and a point is reached at which high gradematerial wil not stand thestrain, but will break.

My present invention provides a way of lessening the strain required topull such cores out of the molded material; thus permitting the use oflonger cores or, for a given 'ength, of cores of greater resiliencyeven, though this means reduced strength. The accompanying drawingsillustrate an embodiment of the invention. Fig. 1 illustrates inlongitudinal section the operation of pulling a flexible core out of themolded conduit. Fig. 2 illustrates the same in crosssection on the line22. Fig. 3 illustrates a modification in section.-

The tubular soft rubber core 1 has'been used to form a conduit 2 in abody of plastic material 3. The conduit is shown with a curvedportion tby way of example. The invention, however, is useful on straight lengthsas well as on curves. The projecting end of the core is pulled in thedirection of thearrow 5. If the length be not too great or the frictiondue to the 'curvein the conduit be 'not. too great, the core can bepulled out without putting a strain on it which is beyond the strengthof the material of which it is composed. Such a pull will diminish thecross-section and break the ad'- hesion of the rubber to the surroundingconcrete progressively backward along the length-of the conduit. andpermit the withdrawal of the core. I

But where the strainrequired is beyond the strength of the materiala-special means is used or breaking the adhesion between the tube andthe surrounding wall at least sufiiciently .to permit the withdrawal ofthe core under a tension less than its breaking strength. The adhesionmay readily be broken to a considerable extent by thrusting a nozzle 6between the core and the sur-' rounding wall at the exposed end of the.conduit and forcing air or water or other lubr1cant into the spacebetween the core and the surrounding wall. The nozzle may be made ofiron pipe or any other suitable material. will force its way between thecore and the surrounding wall backward along the length of the coreescaping into the rear end of the conduit as indicated by the arrows 7.The mere loosening of the core in this way will sometimes besuflicient, theoperation being The air or other fluid introducedcompleted before the core is pulled. But

pressing the latter in the direction of its withdrawal.

According to Fig. the nozzle .6 is con-- nected at its rear end to twobranch pipes 7 and 8, theformer for air and the latter for generally itwill be preferable to continue water, with a cock 9- for cutting oif thewater.

Instead of water, oil or other liquid lubricant may be used.

With this apparatus, according to the circumstances of the case, air,may be used alone to release the core from the surrounding wall, orwater (or other liquid) may be used alone, or the two may be supplied atthe same time. I have found it particularl advantageous to first forcealiquid through the nozzle and th follow this with Although I havedescribed with great particularity' of detail a certain embodiment of myinvention, yet it is not to be understood therefromthat the invention isrestricted 'to the particular embodiment of the invention disclosed.Various modifications there- What I claim is material by means .of aflexible core, the

method of withdrawal which consists in.

forcing a lubricating fluid into the space be- 1. In the molding ofconduits in plastic tween the core and the surrounding-wall so as toflex the core to break the adhesion While pulling the corelongitudinally to withdraw it from the conduit. 7

2. In the molding of conduits in plastic material by the use of aflexible tubular highly resilient core, the method of Withdrawing thecore which consists in the foreing of a fluid between the outside of thecore and the surrounding wall so as to break their adhesion to eachother and simultaneously pulling the end of the core so as to cause itto contract in cross-section and thus augment the breaking of itsadhesion to the surrounding Wall. a

3. In the molding of conduits in plastic material by means of a flexiblecore, the method of withdrawal which consists in the forcing of a liquidand air into the space between the core and the surrounding Wall.

In Witness whereof, I have hereunto signed my name.

THOMAS E; MURRAY.

